Drive Train Of An All-Wheel Drive Vehicle

ABSTRACT

The drive train of an all-wheel drive vehicle comprises a transfer case ( 2 ) that is connected to the motor block ( 1 ), a driven front axle ( 6 ), a driven rear axle ( 4 ), the drive shafts ( 3, 5 ) and a control device ( 15 ). To vary the torque distribution between the axles ( 4, 6 ) from 0 to 100%: a) the transfer case ( 2 ) has a drive-through shaft ( 22 ) that has a drive connection both with the motor block ( 1 ) and the drive shaft ( 3 ) that leads to the rear axle ( 4 ), said drive-through shaft ( 22 ) having a drive connection with the drive shaft ( 5 ) that leads to the front axle ( 6 ) by means of a first friction clutch ( 23 ) that determines the torque applied to the front axle ( 6 ) and a displacement drive ( 26, 27, 28 ); and b) the rear axle ( 4 ) is equipped with an additional adjustable drive unit ( 7 ) comprising a second friction clutch ( 43 ), which is used to control the torque applied to the rear axle ( 4 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/AT2005/000057, filed Feb. 22, 2005, and which claims the benefit ofAustrian Utility Model No. GM 128/2004, filed Feb. 23, 2004. Thedisclosures of the above applications are incorporated herein byreference.

FIELD

The invention relates to a drive train of an all-wheel drive vehicleconsisting of a transfer case adjoining the engine transmission block, adriven front axle and a driven rear axle, the drive shafts leading fromthe transfer case to the axles and a control device, with the torquemetered to the drive shafts being able to be regulated by variableloading of friction couplings.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

In currently common drive trains of all-wheel vehicles, only the torquechanneled off for the drive of the front axle is controlled by means ofa friction coupling. In all-wheel vehicles of the latest generation,however, the torque metered to both axles should be controllable overthe total range from 0 to 100 percent. In this manner, the torquemetered to the front axle cannot only be regulated in a range from zeroup to a proportion fixed by the design and manner of construction, whichlies at around 50%, but from 0 to 100%, that is from purely rear wheeldrive to purely front wheel drive. All-wheel drive can thus also satisfyall dynamic driving demands and safety demands for fast road drivingbeyond off-road operation. This also includes the compatibility withelectronic systems which act on the brakes of the vehicle. The term“torque vectoring” has become common for this in the technical world.

A drive train of this type is known, for instance, from U.S. Pat. No.4,709,775. In this, the transfer case adjoining the engine transmissionblock contains two friction couplings, one in the path to the driveshaft of the front axle and one in the path to the drive shaft of therear axle. Transfer cases of this type are bulky, expensive and complexassemblies. Above all the substantial requirement of construction spaceis very problematic subsequent to the transmission, where it is anywayvery tight.

A drive train for all-wheel vehicles having two or even four couplingunits which meter a regulatable torque to each axle or to eachindividual wheel, is known from DE 38 14 435 Each coupling unit consistsof a controllable liquid friction coupling and of a friction couplingwhich can be engaged and disengaged, that is a non-controllable frictioncoupling, for the bridging of the first. The construction effort and thespace requirements as well as the regulation problems of this solutionare prohibitive. Due to the diversion via the controllable liquidfriction coupling, an accurate and fast control is also not evenpossible.

A drive train is known from U.S. Pat. No. 5,119,298 comprising atransfer case which drives through rigidly to the rear axle and channelsoff the torque for the front axle by means of the friction coupling.This drive train belongs to the older generation of drive trains whichdo not permit any variation in the torque distribution between 0 and100%, but it does show the construction of a transfer case customary insuch drive trains.

SUMMARY

It is therefore the aim of the invention to set forth a drive trainwhich permits the variation of the torque distribution between 0 and100% with a simpler and more space-saving construction and low costs,and indeed fast and accurately.

In accordance with the invention, this is achieved in that the transfercase has a drive through shaft which is connected drivewise to theengine transmission block, one the one hand, and to the drive shaftleading to the rear axle, on the other hand, said drive through shaftbeing connected drivewise to the drive through shaft leading to thefront axle via a coaxial friction coupling determining the torquemetered to the front axle and via an offset drive and in that a furtherregulatable drive unit having a friction coupling is provided at therear axle which regulates the torque metered to the rear axle.

A customary transfer case such as is used in drive trains of the oldergeneration without the torque distribution variable between 0 and 100percent can thus be used as the transfer case.

They are thereby tested drive components which are cheap due to thelarge volumes and which take up only a little construction space in thelongitudinal direction of the vehicle and upwardly. The furtherregulatable drive unit having a friction coupling at the rear axle canbe of any desired construction type and actuation type; it can easily beaccommodated in the vicinity of the rear axle differential. In addition,a better axle load distribution is also thereby attained.

The actuators of the two friction couplings are preferably of the sametype and are controlled from a common control device. Actuators of thesame type respond to control signals of the same type. A single controldevice which controls both couplings simultaneously is therebysufficient.

In a preferred embodiment, the further friction coupling is driveconnected to the first drive shaft, on the one hand, and to thedifferential of the rear axle, on the other hand, and is accommodated ina housing in a unit construction block with the housing of thedifferential. The construction combination in one housing complexprovides further economy of space and a reduction in costs by a commonutilization of bearings and lubrication devices.

In a further development of the invention and while utilizing thepossibilities opened up by it, the couplings can be designed such thatthe transfer casing and the drive unit have a number of same parts.These can be mechanical parts of the coupling, the actuators and, withcorrespondingly disposed separation joints, also housing parts. It isalso within the framework of the invention to provide a parking lockgear, downstream of the friction coupling in the force-flow direction,in the transfer case or in the drive unit with the further frictioncoupling. Such a one is considered necessary in drive trains without acompulsory connection to the road as a safety measure. This is also whyit is disposed downstream. It can be accommodated particularlypractically here or there in a drive train in accordance with theinvention.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 schematically illustrates a drive train in accordance with theinvention;

FIG. 2 details A and B enlarged and in somewhat more detail.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

In FIG. 1, an all-wheel drive motor vehicle is reduced to its drivetrain. An engine transmission unit 1 is connected to a transfer case 2.A first drive shaft 3 leads from this to the rear axle 4 and a seconddrive shaft 5 leads from this to the front axle 6. The first drive shaft3 leads into a drive unit 7 which is adjoined by a rear axle drive 8with a rear wheel differential for the drive of the wheels of the rearaxle 4. The second drive shaft 5 leads into a front axle drive unit 9with a front axle differential.

The transfer case 2 and the drive unit 7 include controllable couplings(see FIG. 2) which can each be actuated by means of a first actuator 11and of a second actuator 12. Position sensors 13, 14 are attached to theactuators 11, 12. They generate position signals for a common controldevice 15 which controls the actuators 11, 12. The control device 15 isconnected via a CAN bus 16 to, inter alia, an ABS control device 17 oranother electronic brake or drive stability control.

In FIG. 2, the transfer case 2 and the drive unit 7 are shown somewhatmore accurately, with bearings and details not essential to theinvention, however, being omitted. The first drive shaft 3 and thesecond drive shaft 5 are shown broken open here and are connected viauniversal joints 3′ 5′ or the like to the transfer case 2 or the driveunit 7. The transfer case 2 is accommodated in a housing 20 connected tothe engine transmission block 1 by means of a flange 21. A firstcoupling 23 is arranged on a drive through shaft 22 and is a frictioncoupling having multiple inner or outer disks. It furthermore consistsof a coupling bell 24, rotationally fixedly connected to the drivethrough shaft 22, on the primary side, and of an inner coupling part 25,on the secondary side, which is a hollow shaft supported on the drivethrough shaft 22 here. The hollow shaft is rotatably fixedly connectedto or integral with a first sprocket 26 which, via a chain 27 or thelike, drives a second sprocket 28 which is rotationally fixedlyconnected to the second drive shaft 5. The sprockets 26, 28 and thechain 27 form an offset drive which could equally easily be made only bytoothed wheels or other transmission means.

The coupling 23 is actuated by the actuator 11, for example, viaarticulated jacks 32 and ramp rings 31.

The drive unit 7 is accommodated in a housing 40 which is integral withor fixedly connected to a housing 41 of the rear axle drive 8. The firstdrive shaft 3 merges here, at the universal joint 3′ into an input shaft42 which leads to a second coupling 43 which is again also a frictioncoupling with multiple inner and outer disks. It furthermore consists ofa coupling bell 44 rotationally fixedly connected to the input shaft 42and of an inner coupling part 45 which simultaneously forms the shaftfor a pinion 46 which acts on the rear axle differential 48 via a ringgear 47. This coupling is actuated in a controlled manner by the secondactuator 12 via a lever 52 and ramp rings 51.

It can also be recognized in FIG. 2 that the two controllable frictioncouplings 23, 43 are of the same construction, apart from the differencebetween the inner coupling part 25 of the first coupling 23 and theinner coupling part 45 of the second coupling 43 forming the pinionshaft. The actuators 11, 12 and the levers 32, 52 as well as the ramprings 31, 51 are likewise identical components.

Overall, a simple and nevertheless complete solution is provided by thedivision of the function of a complex and bulky assembly developedspecifically for “torque vectoring” into two simple and largelyconventional units arranged separately from one another. This solutionis much cheaper and has more economy of space due to the largelyconventional part units which can be produced in large series.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A drive train of an all-wheel drive vehicle comprising: a transfercase adjoining an engine transmission block, a driven front axle and adriven rear axle, drive shafts leading from the transfer case to theaxles, and a control device, with torque metered to the drive shaftsbeing able to be regulated by variable loading of friction couplings,wherein a) the transfer case has a drive through shaft, which isconnected drivewise to the engine transmission block, on the one hand,and to the drive shaft leading to the rear axle, on the other hand, saiddrive through shaft being connected drivewise to the drive shaft leadingto the front axle, via a first friction coupling determining the torquemetered to the front axle and via an offset drive; and wherein b) afurther regulatable drive unit having a second friction coupling isprovided at the rear axle and regulates the torque metered to the rearaxle.
 2. A drive train in accordance with claim 1, wherein actuators ofthe two friction couplings are of the same type and are controlled froma common control unit.
 3. A drive train in accordance with claim 1,wherein the second friction coupling is connected drivewise to the firstdrive shaft, on the one hand, and to the differential of the rear axle,on the other hand, and is accommodated in a housing in a unitconstruction block with the housing of the differential.
 4. A drivetrain in accordance with claim 1, wherein the transfer case and thedrive unit have a series of common parts.
 5. A drive train in accordancewith claim 1, wherein a parking lock gear is provided, downstream of oneof the friction couplings in the force-flow direction, in one of thetransfer case and the drive unit with the further friction coupling.